1. Field of the Invention
The invention relates to a vacuum cleaning tool for a vacuum cleaning device comprising a housing in which a brush chamber and a turbine chamber are provided. A working roller, in particular, a brush roller, is arranged in the brush chamber transversely to the working direction of the suction cleaning tool. The working roller penetrates with a peripheral portion a suction slot provided in the bottom of the brush chamber. An air turbine is arranged in the turbine chamber for driving in rotation the working roller. A vacuum air flow of the vacuum cleaning tool enters the brush chamber via the suction slot, flows into the turbine chamber via an intake window provided in a partition between the brush chamber and the turbine chamber, and exits from the turbine chamber through an outlet window of a vacuum connector. Between neighboring vanes of an annular vane arrangement of the air turbine free flow paths to a vane-free center of the air turbine are formed; the vacuum airflow passes through the vane-free center of the air turbine along its path from the intake window to the outlet window of the vacuum connector.
2. Description of the Related Art
A vacuum cleaning tool of this kind is known from U.S. Pat. No. 5,249,333. A brush chamber and a turbine chamber are formed in the housing. A brush roller is rotatably supported in the brush chamber transversely to the working direction of the suction tool. A peripheral portion of the brush roller penetrates with its bristles through the suction slot provided in the bottom of the brush chamber in order to mechanically act on the floor surface to be cleaned. In the turbine chamber an air turbine is arranged which drives rotatably the brush roller by means of a belt drive. The vacuum airflow enters the vacuum cleaning device through the suction slot in the brush chamber, flows via an intake window in a partition between the brush chamber and the turbine chamber into the turbine chamber, and flows out of the turbine chamber via an outlet window which is provided in a vacuum connector. When doing so, the vacuum airflow flows to the vane-free center of the air turbine between neighboring vanes of an annular vane arrangement of the air turbine and flows again through the annular vane arrangement along its exit path when exiting through the outlet window. As a result of this flow path, a strong power output at the air turbine is obtained, wherein power magnitudes can be achieved matching those of an electric motor used in vacuum cleaning tools.
It is an object of the present invention to optimize the power output of a direct flow turbine in order to ensure even for a weaker vacuum airflow a strong power output and thus a powerful drive action on the working roller.
In accordance with the present invention, this is achieved in that in the flow direction of the vacuum airflow the outlet window of the vacuum connector is positioned higher than the intake window of the partition, in that the annular vane arrangement has approximately 10 to 14 vanes, in that an imaginary connecting line between approximately the center of the intake window and approximately the center of the outlet window intersects the cross-section of the air turbine as a secant, and in that in the circular arc of the circle segment separated by the secant approximately four to six vanes of the annular vane arrangement of the air turbine are positioned.
For an optimal use of the energy of the vacuum airflow by means of the air turbine it must be firstly ensured that in the flow direction of the vacuum airflow the outlet window is positioned higher than the intake window. The annular vane arrangement of a suitable air turbine should in this respect have approximately 10 to 14 vanes which are arranged uniformly about the circumference with an equidistant circumferential spacing to one another. The position of the intake window allowing flow into the turbine chamber and of the outlet window allowing the flow to exit the turbine chamber as well as the arrangement of the air turbine between these two windows positioned at different levels should be such that an imaginary connecting line between the center of the intake window and approximately the center of the outlet window intersects the cross-section of the air turbine as a secant. In the circular arc of the circle segment separated by the secant, advantageously approximately four to six vanes of the annular vane arrangement of the air turbine are to be positioned. This means that the length measured in the circumferential direction of the circular arc of the circle segment separated by the secant is identical to the circumferential distance between approximately five successively arranged vanes. With such a configuration the vacuum airflow will enter approximately at vane I and will exit at the level of the fifth vane V leading in the rotary direction.
A further configuration of the invention provides that the height of the intake window and the height of the outlet window within the housing are adjusted relative to one another such that a connecting line between the upper edge of the intake window and the upper edge of the outlet window extends below the hub of the air turbine. This ensures that the hub of the air turbine is not positioned in the direct flow path of the vacuum airflow flowing through the turbine center.
The surface area of the circle segment separated by the connecting line can correspond approximately to 30% to 45% of the cross-sectional surface area of the air turbine.
An excellent power output has been observed when the vanes of the annular vane arrangement are positioned relative to a radial line through the base of the vane at an angle of approximately 35xc2x0 to 55xc2x0, preferably 45xc2x0. The vanes are curved in the direction of rotation wherein the annular vane arrangement extends across a radial height of at least 30% of the radius of the air turbine.
In order to ensure entry of the vacuum airflow into the center of the air turbine, the mantle surface of the air turbine is positioned at a minimal spacing relative to the turbine chamber bottom. The arrangement of the intake window is such in this connection that its lower edge is positioned approximately at the level of the chamber bottom and the upper edge of the intake window is positioned approximately below the lower edge of the outlet window.
In a further configuration concerning the position of the air turbine in the turbine chamber, it is advantageous to position the axis of rotation, even better, the hub of the air turbine, in the vicinity of the bisecting line which divides the angle, in particular, a right angle, between the partition at the level of the intake window and the chamber bottom. In particular, the bisecting line can be a tangent on the hub of the air turbine wherein the hub is positioned at a side relative to the bisecting line facing the turbine chamber bottom.
For assisting the guiding action of the airflow, it may be provided to configure the turbine chamber bottom in the outflow area of the vacuum airflow from the turbine chamber as a ramp ascending toward the outlet window. Preferably, a groove is provided within the ramp which extends in the flow direction of the vacuum airflow. Its edge facing the outlet window in the flow direction of the vacuum airflow at least substantially covers the housing edge of the outlet window.